10.1021/jp4125342.s001
James Hooper
James
Hooper
Tyson Terpstra
Tyson
Terpstra
Andrew Shamp
Andrew
Shamp
Eva Zurek
Eva
Zurek
Composition
and Constitution of Compressed Strontium
Polyhydrides
American Chemical Society
2014
SrH 4 stoichiometry
150 GPa
density
SrH 6 stoichiometry
helice
formation
hydrogenic
phase
configuration
Compressed Strontium PolyhydridesThe structures
2014-03-27 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Composition_and_Constitution_of_Compressed_Strontium_Polyhydrides/2311336
The
structures of the strontium polyhydrides, SrH<sub><i>n</i></sub> with <i>n</i> > 2, under pressure are studied
using
evolutionary algorithms coupled with density functional theory calculations.
A number of phases with even <i>n</i> are found to be thermodynamically
stable below 150 GPa. Particularly interesting is the SrH<sub>4</sub> stoichiometry, which comprises the convex hull at 50, 100, and 150
GPa. Its hydrogenic sublattice contains H<sub>2</sub> and H<sup>–</sup> units, and throughout the pressure range considered, it adopts one
of two configurations which were previously predicted for CaH<sub>4</sub> under pressure. At 150 GPa, the SrH<sub>6</sub> stoichiometry
has the lowest enthalpy of formation. The most stable configuration
assumes <i>P</i>3̅ symmetry, and its lattice consists
of one-dimensional H<sub>2</sub>···H<sup>–</sup> hydrogenic chains. Symmetrization of these chains results in the
formation of <sub>∞</sub><sup>1</sup>[H<sup>δ−</sup>] helices, which are reminiscent
of the trigonal phase of sulfur. The <i>R</i>3̅<i>m</i>-SrH<sub>6</sub> phase, which is comprised of these helices,
becomes dynamically stable by 250 GPa and has a high density of states
at the Fermi level. We explore the geometric relationships between <i>R</i>3̅<i>m</i>-SrH<sub>6</sub> and the Im3̅<i>m</i>-CaH<sub>6</sub> and <i>Imm</i>2-BaH<sub>6</sub> structures found in prior investigations.